Dry Reforming of Methane over Rare-Earth Metal Oxide Ni-M-Al (M = Ce, La) Catalysts

Dry reforming of methane (DRM) was investigated using Ni-M oxide catalysts prepared by solution combustion synthesis (SCS) and compared with Ni/α-Al₂O₃ synthesized by impregnation. According to X-ray diffraction, fresh oxide Ni-La and Ni-Ce catalysts displayed low crystallinity, which was improved after DRM, accompanied by the appearance of metallic Ni. Ni-Ce-Al and Ni-La-Al catalysts formed, respectively, CeAlO₃ and LaAlO₃ phases during the reaction. For studied catalysts featuring low surface areas ranging from 3 to 12 m²/g, the average metal particle sizes were 12-32 nm according to transmission electron microscopy, with the particles growing larger with time-on-stream (TOS) apart from Ni-α-Al₂O₃. DRM tests were conducted for different TOSs, demonstrating that the highest CH₄ transformation rate was concomitant with the highest deactivation rate during 30 min of time-on-stream. The most stable performance in temperature stability experiments was demonstrated by the Ni-Ce-Al catalyst, for which, similar to other catalysts, the H₂/CO ratio remained close to unity. In long-term stability tests, the Ni-Ce-Al catalyst displayed a 3.1-fold higher turnover frequency (TOF) compared with Ni-α-Al₂O₃, with no significant deactivation. The TOF values were comparable to the literature, highlighting the potential of SCS as an alternative approach for synthesis of DRM catalysts.